package com.ysjt.exam.utils;

import java.security.MessageDigest;

import java.util.Random;

import java.security.NoSuchAlgorithmException;

import org.apache.commons.codec.binary.Hex;

/**
 * @author yuxiaofei
 * <pre>
 *
 * </pre>
 * @date 2019/9/16 11:18
 */
public class MD5Util {

    public static String generate(String password) {

        Random r =new Random();

        StringBuilder sb =new StringBuilder(16);

        sb.append(r.nextInt(99999999)).append(r.nextInt(99999999));

        int len = sb.length();

        if (len <16) {

            for (int i =0; i <16 - len; i++) {

                sb.append("0");

            }

        }

        String salt = sb.toString();

        password = md5Hex(password + salt);

        char[] cs =new char[48];

        for (int i =0; i <48; i +=3) {

            cs[i] = password.charAt(i /3 *2);

            char c = salt.charAt(i /3);

            cs[i +1] = c;

            cs[i +2] = password.charAt(i /3 *2 +1);

        }

        return new String(cs);

    }

    /**

     * 校验加盐后是否和原文一致

     * @author daniel

     * @time 2016-6-11 下午8:45:39

     * @param password

     * @param md5

     * @return

     */

    public static boolean verify(String password, String md5) {

        char[] cs1 =new char[32];

        char[] cs2 =new char[16];

        for (int i =0; i <48; i +=3) {

            cs1[i /3 *2] = md5.charAt(i);

            cs1[i /3 *2 +1] = md5.charAt(i +2);

            cs2[i /3] = md5.charAt(i +1);

        }

        String salt =new String(cs2);

        return md5Hex(password + salt).equals(new String(cs1));

    }

    /**

     * 获取十六进制字符串形式的MD5摘要

     */

    private static String md5Hex(String src) {

        try {

            MessageDigest md5 = MessageDigest.getInstance("MD5");

            byte[] bs = md5.digest(src.getBytes());

            return new String(new Hex().encode(bs));

        }catch (Exception e) {

            return null;

        }

    }

    public static void main(String[] args) {

        String password =generate("20180920");

        System.out.println(verify("20180920", password));

    }

}